log4go | Logging package similar to log4j for the Go programming

func (log Logger) Warn(arg0 interface{}, args ...interface{}) error {
const (
    lvl = WARNING
)
var msg string
switch first := arg0.(type) {
case string:
    // Use the string as a format string
    msg = fmt.Sprintf(first, args...)
case func() string:
    // Log the closure (no other arguments used)
    msg = first()
default:
    // Build a format string so that it will be similar to Sprint
    msg = fmt.Sprintf(fmt.Sprint(first)+strings.Repeat(" %v", len(args)), args...)
}
log.intLogf(lvl, msg)
return errors.New(msg)
}

func (log Logger) Info(arg0 interface{}, args ...interface{}) {
const (
    lvl = INFO
)
switch first := arg0.(type) {
case string:
    // Use the string as a format string
    log.intLogf(lvl, first, args...)
case func() string:
    // Log the closure (no other arguments used)
    log.intLogc(lvl, first)
default:
    // Build a format string so that it will be similar to Sprint
    log.intLogf(lvl, fmt.Sprint(arg0)+strings.Repeat(" %v", len(args)), args...)
}